1961 MKII Valve clearance after rebuild - just a sanity check needed

Hello folks -

Doing a valve clearance check on my '61 MKII - when I bought the car, I was told the head and timing components been rebuilt / replaced in the last 2 years, with little miles on them - and from looking at the engine, I’ve no reason to think that’s not accurate. That said, I was getting a loud tick from a forward intake valve and the car has a miss at idle, so I checked the valve clearances today - order here is #1 through #6 respectively:

Intake: .001, .003, .003, .003, .009, .0015 Exhaust: .008, .006, .009, .005, .007, .006

The good news here is that the tappety intake valve is right where I pegged it with my stethoscope - BUT - I wasn’t expecting the generally tight intake clearances - .004 is the goal and I believe slightly more clearance is preferred over slightly less. Intakes on #1 and #6 were incredibly tight, I guessed at #1 because frankly I couldn’t get any feeler gauge to clear.

Exhaust side is a bit better, at least two are dead on, and one is close enough, but the other three are at least .002 off in one direction or the other.

SO here is my question - Is there any reason why a recently rebuilt head should have tighter clearances, or is this just a case where the builder got it wrong, and I need to correct it. What I don’t want is to spend the time making them right, only to discover that “the clearances are supposed to be tight following rebuild and they settle in by -.002 after 2000 miles”…or something like that. I’ve not heard that to be the case, but want to check before I take the time to switch everything around.

Oh…and gather up 6 billion shims…from…somewhere…


Nope those clearances are crap. Set them to the factory limits.

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I did my my Mk2 a couple of years ago. So after 3000 miles I’m still in spec - target set them about 0.001" over spec. Paul.

For a newbie - the measurement is taken with each lobe facing opposite to valve stem, right ? Not some predefined timing position, like valve passing (TDC) or else … ?

Disappointing. But fixable.

As long as the lobe is roughly pointing away from the tappet it’s close enough.
Can you turn the #1 tappet or slide anything beneath at all? Do you have compression on that cylinder?
Good thing you checked the clearances, redo them. Either someone lends you their kit or you buy and sell a set when you’re done. You can also order the shims you need but you will probably have to set a few again anyways, it’s not always perfect on the first try.


You can order the shims individually, and maybe swap around some you already have to get closer, I have found that you can get a variation when measuring, who knows why

I suggested to our Jag Club to have a “Shim Library” whereby a set was purchased by the Club, and any member who uses some re-orders what they used, but the vast majority of our Club members dont get down to this level, so the idea was not accepted

I still think its a good idea, and better than “wasting” our built up cash surplus on the the trinkets they do. (Most of our Club members own newer Jags)

I have quite a few shims in a little jar

I always set the 4/6 engines to a spec of 6/8: the increased noise is minimal, and the increase in service interval is worth it.


Thanks all - I’ll be getting the cams out today and measure the shims - hopefully at least a few will work for a different valve, but we’ll see. In terms of the specs, I’m going to try get close to .004 / .006 but I’m not going to worry if I’m .001 out to the wider side - I don’t want the gaps tighter, but the goal here is good, not perfect.

Well, phase one is complete. Cams out, shims measured. Unfortunately, only two will work for another valve - so I ordered the rest.

Went fairly smooth, after 2 major near catastrophes…

  1. In all the videos I’ve watched, it was necessary to tap the sprockets off the cam after the bolts were removed, so I didn’t see any issue in removing the bolts before then rolling the engine around to TDC - well, in my case, the sprockets were only two happy to fall off on their own, except that I didn’t notice until I’d rolled the engine about 1/8 of a turn - so basically the sprockets were moving, but the cams didn’t. Fortunately, I did notice, and was able to get everything back in order. I then put the bolts back in, took one out (each side) at a time and then rolled the motor back to TDC, and got the final two bolts. I made sure both cams were TDC with the tool, and that the balancer also showed TDC and that the distributor was also pointed correctly for TDC. Luckily, I hadn’t rolled the motor that far, so it was relatively easy correct.

  2. In my haste to fix the issue, when I realized the motor was turning but the sprockets had disengaged from the cams, I made a BIG mistake - I neglected to put a rag in the hole around the sprocket - and you guessed it, the bolt flipped out of my fingers…and vanished. I literally couldn’t believe it - I had rags everywhere else, and I know better, but bam…in an instant. I looked all over, could not find it anywhere. I was about to get my boroscope and go looking inside when I decided to fix the timing error first, and in the process of nudging the engine over, the bolt eventually fell out from who knows where, and landed under the car - you could have heard the sigh of relief from Mars.

Anyway - shims ordered, plus a few to either side in some cases. Knowing my luck, they’ll be back-ordered until December. :wink:


After those two near misses, it sounds like it’s Lottery ticket time :slight_smile:

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@JonV2 : No kidding. Despite owning now 4 MKIIs and other jaguar’s besides for decades, I’d never actually done the valve adjustment myself before, so this was also a maiden voyage into the unknown…

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Make a list of valve clearances, shim thickness, and thickness required for each valve. Ive found by juggling shims around I’ve only ever needed 2 - 3 new ones.

If you can get two guys to do it at the same time you probably won’t need any new shims…speaking from experience.

Well, just an update to close the loop on this one -

I did all my measuring, ordering, etc and I think I’m done with the job for now - just need to close-up the cam covers and see how she runs.

One tip I would give, is to double check your old and new shim sizes…yes…even the new ones. I double checked all the new shims I bought from Moss and found almost all of them to be 0.0005 less than the label indicated, but some were 0.001 off, sometimes even among the same size shim. So for example I had 6 shims labeled as 0.091, but found most were actually 0.0905, similarly for the .092 shims - most were really 0.0915. There were some shims however that were off by a full 0.001. This may not really seem like much, but we’re only looking at 0.004 / 0.006 clearance in the first place, and if you cannot hit that spec exactly and plan to accept a slight +/- on the spec, its critical to verify the shim.

I ultimately made a spreadsheet that looked at current shim, current clearance, calculated optimal replacement shim to hit the specified clearance and then provided a cell where I could enter the shim I actually used, and see what that meant for the actual clearance achieved. The second tip I’d provide however, is that math lies. :wink:
I guess its because you are dealing with such small clearances, but by the time you’ve taken off the cam, replaced the shims, reinstalled the cam and torqued to spec, things change just a bit. All my clearances ended up within 0.001 of the intended target, but only 7 were actually dead on to what my spreadsheet indicated.

Overall, every valve is within .001 or less of target, and I’m happy enough with that. The only two of minor concern are both cylinder #1:

INTAKE: I’m making a guess at 0.0038. Target = 0.004. I was able to shove a 0.004 feeler between the cam and tappet, but only by wiggling it a bunch and trying to force it through - as much as you can with a piece of metal only 0.004 thick. So technically I got it in, but its clearly tighter than the typical feeler gauge “resistance”, but a 0.003 gauge felt on the loose side, so I suspect we’re 0.0035+

Exhaust: Again a guess at 0.0055. Target = 0.006. As with the above, I was able to push a 0.006 gauge in the space, but took some wiggling - though not as much as on the intake side. A 0.005 gauge felt loose, so its around 0.0055. I’ve read that 0.001 in either direction will not harm anything, and that in fact clearances will open up when warm, so I suspect this is not going to be an issue, and I really don’t want to disassemble everything for the sake of +0.0002 and +0.0005 clearance. I feel its just as likely that in the quest to fix those two minor discrepancies, I’ll end up with more discrepancies in other valves since measurements will again be a little off after removing and replacing the cams.

Granted there are those that seek perfection, but I’m all for being satisfied with"good enough".


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Now someone will say that you can in fact set them up 6/8, but I would have done exactly what you did. Sounds good to me, enjoy the car.
And your two near misses… nice. Sounds a lot like me when I did it at the end of a long night around 5 am last year!

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Should work fine: I would recheck everything after 1000 miles.


I agree with Paul. You’ve obviously made a lot of effort to get things as close as you can and I’m sure you car will be fine.

Personally, unless you still have a noisy tappet, I wouldn’t bother to recheck them.

I have always thought that once set up correctly, the valve clearances wont change, and can be neglected for years and tens of thousands of miles.
Is this assumption correct?

Yes… and no.

After setup, there is always a settling-in period: most always no significant change occurs, but, there might be changes in clearances that can happen.

Ergo, why to do a check after 1000 miles: at that time, if no changes occur, most always it’s good for many miles.